Soil Properties Following Reforestation Or Afforestation Of Marginal Cropland

Aims Reforestation or afforestation of marginal agri- cultural lands offers opportunities to sequester soil organic carbon (SOC), improve the quality of degrad- ed soils, and provide ecosystem services. The objec- tives of this study were to identify the extent and distribution of marginally productive cropland in the state of Iowa and to quantify the changes in SOC and relevant soil properties following tree planting. Methods A geographic information system (GIS) analysis was used to identify 1.05 million ha of mar- ginal cropland within the state. Soil samples were collected from four locations with (<51 yr-old) forest plantations and adjacent crop fields. Soil samples were analyzed for SOC, total nitrogen (TN), pH, cation exchange capacity (CEC), ammonium acetate- extractable K, Ca, Mg, and Na, and particle size. Results The forested soils had 30.0±5.1 % (mean ±standard error) more SOC than the tilled cropland. The average annualchangeinSOC following treeplant- ing was estimated to be 0.56±0.05 Mg C ha �1 yr �1 . Differences were observed in several soil properties but strong correlations with SOC content were only observed for bulk density and extractable Ca. Conclusions These results indicate that within 5 dec- ades of tree planting on former cropland or pasture there was consistently and significantly greater SOC in soil beneath the trees.